I have recently trying to flash the B-U585I-IOT02A board by running the 3 scripts generated in the build folder, as I usually do with the STM32L552 board. However, I encountered some unexpected errors as I noticed that the secure and non-secure images were being written to external flash address spaces. I quickly noticed that this was happening because the "flash_layout.h" file defines the variable "EXTERNAL_FLASH". Additionally, the "image_macros_to_preprocess_bl2.c" set the image as encrypted by default with "RE_IMAGE_ENCRYPTED= 0X01", causing the "TFM_UPDATE.sh" script to write to the secondary slots. 

I found it quite strange because tf-m presented an off-the-shelf solution for the other board  while for this board it assumes the use of an external flash. 

Nevertheless, I tried to work around these limitations by commenting the EXTERNAL_FLASH variable and assigning the "RE_IMAGE_ENCRYPTED= 0X00" similarly to the stm32l552. This led to the images being written to the primary slots defined in the flash layout, however, in runtime I encountered an error that states "Unable to find bootable image". 

Therefore, my question is: Do I need to make further adjustments, or is it possible that there's a configuration issue that is not compatible with the board?

Best regards,

João Bento